It has an inner layer you can remove!

"Yes!" you cry out, pumping your fist. You'd worried about separating whoever has been wearing Jessica from the real Jessica -- maybe if you'd worn the Jess suit and used the brown "pen" on your new self you'd have known who was wearing Jess but been unable to separate that person from her. Now it'll be easy! You reach through the opening in the Jessica suit's back and into your girlfriend's hollow head, get a grip on the lining that is surely a suit of whoever had been wearing her, and pull out the head of the inner suit.